Burkhard Volland

Charging effect simulation model used in simulations of plasma etching of silicon

Understanding the consequences of local surface charging on the evolving etching profile is a critical challenge in high density plasma etching. Deflection of the positively charged ions in locally varying electric fields can cause profile defects such as notching, bowing, and microtrenching. We have developed a numerical simulation model capturing the influence of the charging effect over the entire course of the etching process. The model is fully integrated into ViPER (Virtual Plasma Etch Reactor)—a full featured plasma processing simulation software developed at Ilmenau University of Technology. As a consequence, we show that local surface charge concurrently evolves with the feature profile to affect the final shape of the etched feature. Using gas chopping (sometimes called time-multiplexed) etch process for experimental validation of the simulation, we show that the model provides excellent fits to the experimental data and both, bowing and notching effects are captured—as long as the evolving prof...

Pattern-generation and pattern-transfer for single-digit nano devices

Single-electron devices operating at room temperature require sub-5 nm quantum dots having tunnel junctions of comparable dimensions. Further development in nanoelectronics depends on the capability to generate mesoscopic structures and interfacing these with complementary metal–oxide–semiconductor devices in a single system. The authors employ a combination of two novel methods of fabricating room temperature silicon single-electron transistors (SETs), Fowler–Nordheim scanning probe lithography (F-N SPL) with active cantilevers and cryogenic reactive ion etching followed by pattern-dependent oxidation. The F-N SPL employs a low energy electron exposure of 5–10 nm thick high-resolution molecular resist (Calixarene) resulting in single nanodigit lithographic performance [Rangelow et al., Proc. SPIE 7637, 76370V (2010)]. The followed step of pattern transfer into silicon becomes very challenging because of the extremely low resist thickness, which limits the etching depth. The authors developed a computer simulation code to simulate the reactive ion etching at cryogenic temperatures (−120 °C). In this article, the authors present the alliance of all these technologies used for the manufacturing of SETs capable to operate at room temperatures.

High-energy ion projection for deep ion implantation as a low cost high throughput alternative for subsequent epitaxy processes

Three-dimensional (3D) doping into depths up to 40 μm is of great interest for numerous device types. In particular, the production of high-power devices requires low cost vertically structured doping. State of the art epitaxial growth combined with diffusion and/or low-energy ion implantation is time consuming and cost intensive. We suggest 3D structured high-energy ion projection implantation as a simple cost effective and reliable alternative. This method allows controlled fast doping with high homogeneity and reproducibility. This article outlines some details of a feasibility study of the technique and discusses advantages and problems.

Experimental setup for characterization of self-actuated microcantilevers with piezoresistive readout for chemical recognition of volatile substances

This paper summarizes our achievements in the development of an advanced microcantilever-based platform for the detection and recognition of various volatile analytes. The implemented microcantilevers include integrated piezoresistive readout, integrated thermally driven bimorph actuator, and a gold pad at the cantilever apex for functionalization toward the detection of specific substances. Up to eight single microcantilevers can be installed and investigated quasisimultaneously in either gas flow or gas/vapor single injection mode. The experimental setup enables the detection of the microcantilever bending via surface stress changes, characterization of either amplitude or phase spectra of the microcantilever, and also calibration of its sensitivity.

Heavy ion projection beam system for material modification at high ion energy

Ion projection techniques have shown promising prospects to applications in direct high energy, high dose, and high quality material modification. The major advantages are a parallel processing for short implantation times and a mask separated from the target, which allows for implantation with high resolution and high quality even under extreme conditions. A system for high beam power has been developed. The key issues of our high energy ion projection system are the single solenoid lens with low imaging aberrations and the stencil mask which has to provide the necessary high resolution features and to withstand a beam power up to 100 W/cm2. A high aspect ratio stencil mask is used for this purpose. The system has a demagnification factor of 16–22 and showed a resolution of 300 nm so far which is close to the physical limit for MeV ions from lateral straggling in the target. The setup, the mask, and some applications are presented.

Raster-Sonden-Mikroskopie mit Cantilever-Arrays (Scanning Probe Microscopy with Cantilever Arrays)

Der Artikel beschreibt die Realisierung von piezoresistiven Cantilever-Arrays für die Raster-Kraft-Mikroskopie. Sensoren für die Raster-Sonden-Mikroskopie (RSM) sind aus physikalischer Sicht faszinierende Mikrosysteme, da sie durch geeignete Kombination von Physik und Technologie ein neues nanoskopisches Materialverständnis ermöglichen. Die Raster-Sonden-Mikroskopie führt nicht nur zur Eröffnung neuer Horizonte für die Grundlagenforschung, sondern bietet auch die Chance, durch die Entwicklung neuartiger Sensoren und Sensorarrays bisher ungenutzte Wirkmechanismen zu nutzen. Physikalische, biologische und chemische Größen und Wechselwirkungen können auf der Basis von Mikro-Biegebalken (sog. Cantilever) durch die Umwandlung in eine mechanische Reaktion (Verbiegung des Cantilevers) sehr effektiv erfasst und dann wiederum in elektronisch verwertbare Signale umgewandelt werden. In diesem Artikel werden die Grundideen zur Realisierung von selbstoszillierenden piezoresistiven Cantilever-Arrays als System vorgestellt, mit denen Bilder mit hoher Geschwindigkeit aufgenommen werden können. This paper reports on to the realization of piezoresistive cantilever-Arrays used in scanning probe microscopy (SPM). Sensors for the SPM are peculiar microsystems since the combination of physical and microtechnological principles allows to gain an insight into the material science at nanoscale. Moreover SPM technology is opening new horizons in fundamental research and gives a chance to employ new interaction principles for the realization of new sensors and sensor arrays. Physical, biological, and chemical values and interactions can effectively be detected and analyzed using cantilevers, where the nanomechanical interactions can be transformed into an electric signal. The basic issues for the realization of a complete system of self-actuated, piezoresistive cantilever arrays are described.

Determination of residual stress and elastic constants of silicon open stencil masks for ion projection lithography

The Ion Projection Lithography is one challenge for a semiconductor technology, starting with sub micron structures, which are beyond the facilities of conventional UV lithography. Within this field of research one of the most critical aspects is the development of stencil mask, because the stress formation during the various process steps affects the critical dimensions of the structures to be written. In this paper different methods for the determination of residual stress and elastic constants of thin membranes of doped silicon are reviewed and additionally, a novel technique is presented. First experimental result show, that they are quite different from the values of the bulk material.

Fabrication of optical nanodevices through field-emission scanning probe lithography and cryogenic etching

Sub-10 nanometer lithography is opening a new area for beyond-CMOS devices. Regarding to single nano-digit manufacturing we have established a new maskless patterning scheme by using field-emission, current controlled Scanning Probe Lithography (cc-SPL) in order to create optical nanodevices in thin silicon-on-insulator (SOI) substrates. This work aims to manufacture split ring resonators into calixarene resist by using SPL, while plasma etching at cryogenic temperatures is applied for an efficient pattern transfer into the underlying Si layer. Such electromagnetic resonators take the form of a ring with a narrow gap, whose 2D array was the first left-handed material tailored to demonstrate the so-called left-hand behavior of the wave propagation. It is shown that the resonance frequency can be tuned with the feature size of the resonator, and the resonance frequency can be shifted further into near infrared or even visible light regions.